Quorum sensing is a process of bacterial cell-cell communication that involves production and detection of secreted signal molecules called autoinducers. Quorum sensing allows bacteria to collectively regulate gene expression and function as multicellular organisms. The model Gram-negative quorum sensing bacterium, Vibrio harveyi integrates information from three different autoinducers, CAI-1, AI-2 and AI-1 that together enable intra- and inter-species communication. I will characterize the AI-1/LuxN sensor interaction and determine how AI-1 alters the signaling properties of LuxN. I will perform structural analyses of apo- and holo- LuxN protein. AI-1 encoded information is integrated with the two other V. harveyi autoinducers to control quorum-sensing behavior. This information converges to regulate expression of four redundant small regulatory RNAs (sRNAs). I will determine how the quorum sensing autoinducers precisely control the expression of the sRNAs. Promoter analysis of the DNA encoding the sRNA regulatory elements suggests that additional transcriptional regulators modulate the level of each sRNA. I will identify and characterize additional regulators of the sRNAs. [unreadable] [unreadable] [unreadable]